1. Field of the Invention
This invention relates to flexible articles and, in particular, flexible articles formed from polyurethanes.
2. Art Background
A variety of consumer products are formed from poly(dialkyl siloxanes)--materials generally denominated silicones. Exemplary of products employing silicones are those having touch sensitive screens or pads that allow users, for example, to select options from a video screen, to dial touch pad telephones or to input computer data. In such applications, the silicones are chosen to furnish a resiliency necessary for deformation to produce a desired result (the selection of or input of data) followed by a return to the original configuration to prepare for subsequent input. Indeed, typically a flexibility in the range 30 to 70 Shore A hardness is considered quite desirable for such applications. (Shore A hardness is defined in ASTM (American Standard Testing Method) D2240.)
The resilient material, e.g. silicone, is typically formed into the desired shape, e.g. tough pad or screen, by compression molding. In this fabrication process a sheet of the silicone is subjected to a mold under high pressure causing permanent deformation of the material sheet into the mold configuration. Although this technique has been widely used, the process is relatively expensive because it includes extensive manual operations, e.g., mixing, compounding, sheeting and vulcanization.
Additionally, there is growing evidence that silicone materials, despite acceptable performance, lose flexibility and stability over extended time periods. Additionally the unreacted oligomers in the silicone tend to exude during use causing electrical contact failure. Thus, it is desirable to find a processing technology for forming resilient products that avoids the expense of compression molding and the difficulties associated with silicone materials.